Pressure pouring tube



Sept. 22, 1910 R, K, MACK 3,529,753

PRESSURE POURING TUBE Filed Jan. 13, 1969 FIG. I

INVENTOR. Royce K. Mack AT T ORNEiY Int. Cl. B67d 5/60 US. Cl. 222-46411 Claims ABSTRACT OF THE DISCLOSURE A refractory pouring tube of thetype employed in pressure casting molten steel from a melt thereof byapplying a superatmospheric pressure to the surface of the melt to forceit upwardly through the tube for discharge into a mold. The tubecomprises a fired inner tubular member of refractory composition, afired outer tubular member of refractory composition within which theinner member is receivable so as to form an annular space between them,and a refractory mortar in the annular space to join the memberstogether. The outer member extends longitudinally of the length of theinner member for at least the length of the tube which is to be immersedin molten steel.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of my prior filed copending parent application S.N.506,095, filed Nov. 2, 1965 and claims an invention disclosed in saidprior copending application. The benefit of the filing date of saidprior application is hereby claimed.

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates torefractory pouring tubes of the type employed in pressure casting moltenmetals.

As is well known, controlled pressure pouring is a direct method ofcasting slabs from a ladle containing molten metal. A cap for sealingthe open top of the ladle, or for sealing a container holding the ladle,is provided with a vertically extending, refractory pouring tube. Inpractice, the tube is oriented with the inlet, or lower end, of the tubeimmersed in the melt; and the outlet, or upper end, extending throughthe cap. Superatmospheric pressure applied to the surface of the meltforces the molten metal upwardly through the pouring tube for dischargeinto a mold.

The success of this pressure pouring method depends for efiiciency andeconomy in no small measure on the durability and dependability of thepressure pouring tube. It is therefore a principal object of the presentinvention to provide a long-lasting refractory pouring tube which can beused for many heats to pour a large number of slabs before it must bereplaced.

Ideally, a pressure pouring tube has a wall of dense, impermeableconstruction in order to resist flow therethrough of the pressurized airor gas used to force molten metal up the tube. In addition, the tubeshould be capable of withstanding not only the thermal shock ofimmersion in 2950 F. molten steel, but also chemical attack from hotslag on its exterior surface, as well as erosion of its internal surfacefrom the flow of hot metal therethrough.

In the course of developing tubes for use with the pressure pouringprocess for pouring molten steel, it was found that a monolithicallyformed tube could not be used to pour more than 30 tons of molten steel.To increase the tonnage the wall thickness of the tube had to UnitedStates Patent 0 3,529,753 Patented Sept. 22, 1970 ice be increased.However, when the wall thickness of the tube was increased, the tubecould not withstand the thermal shock of being immersed in molten steeleven after the tube was preheated to 1800 F. For example, assume amonolithically formed tube having a wall thickness of :1 inches canwithstand the thermal shock of being immersed in molten steel, but ifits wall thickness is increased beyond d inches it cannot withstand theshock. In an effort to increase the life of the tube I experimented witha composite tube comprising an inner cylindricallyshaped member ofmonolithic construction which was receivable within an outercylindrically-shaped member of like construction, assembled them so asto form an elongated annular space between them, and filled the spacewith mortar. With the composite tube I found I could make the wallthickness of each of the members d inches in thickness. Thus the portionof the composite tube which was to be immersed in molten steel couldhave a wall thickness of 2d inches and the pouring life of the tubethereby increased. I believe the reason the composite tube is able towithstand the thermal shock of being immersed in the molten steel isbecause the mortar joint between the inner and outer members allows formovement of the members relative to one another when they are immersedin molten steel. The outer member may be made of a plurality of annulistacked in series as shown in my copending application S.N. 506,095,without departing from the spirit and scope of the invention. Thecomposite tubes have been used to pour up to 200 tons of steel withoutbeing replaced.

Accordingly, the invention comprises, a refractory pouring tube of thetype employed in pressure casting molten steel from a melt thereof byapplying a superatmospheric pressure to the surface of the melt to forceit upwardly through the tube for discharge into a mold. The tubecomprises a fired inner tubular member of refractory composition, afired outer tubular member of refractory composition within which theinner member is receivable so as to form an annular space between them,and a refractory mortar in the annular space to join the memberstogether. The outer member extends longitudinally of the length of theinner member for at least the length of the tube which is to be immersedin molten steel. The outer tubular member may be made up for the desiredheight of a stacked series of annuli joined together with mortar to forman elongated annulus as described in my parent application.

Further, the invention may be said to comprise a tube made entirely ofrefractory materials and immersible in molten steel, comprising, a firstannular member of ceramic refractory composition, a second annularmember of ceramic refractory composition adaptable to receivingtherewith the end of the first member which is to be immersed in moltensteel, the members assembled so as to form an annular space therebetweenwhich extends longitudinally of the length of the tube, and a refractorymortar entirely filling the annular space to join the members together.

The refractory compositions of the tube components including the innerand outer members and the mortar are described more fully in thedetailed description which follows. The method of making the componentsand assembling the same are also described hereinafter in detail.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofpressure pouring apparatus incorporating the pressure pouring tube ofthe present invention;

FIG. 2 is an enlarged view of a fragment of the apparatus of FIG. 1;

FIG. 3 is a vertical sectional view of an enlarged scale of the pressurepouring tube of FIG. 1 in another form; and

FIG. 4 is an enlarged, horizontal sectional view of the pressure pouringtube of FIG. 1, taken along line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, pressurepouring apparatus incorporating the invention may comprise an airtightcontainer for a ladle 12, the container including a vessel body 14provided with a pressurized air inlet 16 and also a cover 18 having acentral hole 19 fitted with a refractory tube 20. The latter serves toconduct molten metal 22 under superatmospheric pressure, say 60 p.s.i.,upwardly from the bottom of the ladle 12 through a suitable gate andpassageway (not shown) to a mold (also not shown). It is the applicationof gas pressure to the surface of the melt 22 that forces molten metalup the tube 20 in the direction of the arrow 38 and into the mold.

The body 14 of the container 10 may be made of concrete and/or steel andof sufiicient size to receive the ladle 12 therein on supporting legs28, with generous clearance on all sides of the ladle. Molten metal 22may be supplied to the ladle 12 from one or more furnaces (not shown).The ladle 12 may be made of refractory and steel material in anysuitable vessel shape which is open at the top, preferably with a sumpformed in the bottom thereof to provide a point from which molten metalmay be withdrawn from the ladle 12.

The mutually facing surfaces 32 of the body 14 and the cover 18 arepreferably frusto conical in order that the cover 18 will seat centrallyon the body 14 in registering, as well as sealing, relationship. Inaddition, an underside portion of the cover 18 positioned above the opentop of the ladle 12 has a suitable insulating refractory lining 34.Carried upright by a centrally apertnred portion of the cover 18 is thepressure pouring tube 20, with its lower or inlet end 36 being adaptedfor reception in the sump 30 and its upper or outlet end 38 extendingupwardly through and beyond the cover 18, as shown.

As shown in FIGS. 1 and 2, the tube 20 depends from a tubular pouringhead 39 and a tapered tubular holder 40. The latter two parts 39 and 40are bolted together at 41 in axial alignment and they are carried on asupporting plate 42 which, in turn, rests on the cover 18 throughresilient members 43. Further provided is a metal bellows type ofexpansion joint 44 which effects a seal between the cover 18 and thepouring head 39, thereby maintaining air or gas pressure within thecontainer 10 despite the hole 19 in the cover 18. A refractory mortarcomposition 45, poured in the tapered annular space between the tube 20and the assembly of the head 39 and the holder 40, adheres to the outersurface of the tube 20 so that the holder 40 holds the tube 20 againstdownward movement by engagement with the mortar filler joint 45. A metalring 46 rests in the mortar composition at the top thereof; and anannular asbestos gasket 47 rests on the top surface of the assembly. Inaddition, a fillet 48 of enamel glaze between the tube 20 and theannular lower end surface of the mortar joint 45 seals the interface andthe end surface of the joint.

A plurality of molds may be used one after the other for pouring slabsby the introduction of molten metal thereto through a mold gate movablefor controlling the flow of discharged molten metal from the tube outlet38. 'Opening the mold gate admits molten metal under pressure to themold cavity until it is filled, after which the gate is closed toprevent further flow of molten metal into the mold cavity.Simultaneously with the closing of the mold, gate pressure is preferablyreduced in the container 10 until the next mold is positioned and readyto be poured.

In one embodiment, the pressure pouring tube 20 of the present inventioncomprises an inner tubular member 54, preferably of cylindrical shape,an outer tubular member 56 may be made up of ring collars or cylindricalannuli 58 stacked one above the other, and a mortar joint 60 between theends of the annuli 58 and an annular mortar joint 62 between the innerand outer members 54 and 56 to join them all together. However, in thepreferred embodiment the outer member 56 is made in the same form as theinner member 54, an elongated annular mem ber molded as a single sectionas shown in FIG. 1. In either embodiment the members 54, 56, 58 are ofmonolithic construction and of sufiicient wall thinness to resist thethermal shock of being immersed in molten steel, at least after thecomposite tube formed thereby is preheated to aproximately 1000 F.However, it is understood that the commercial product need not be sopreheated prior to shipment to the consumer. One embodiment or the othermay be chosen depending on the availibility of capital equipment. Anannular space of from 4, to inches wide between the members 54 and 56has been found suitable to permit the mortar to be introduced by makingit in the consistency of a thin slurry which can be poured into the opentop of the annular space. The entire tube 20 including the mortar forthe joints 60 and 62 is made of refractory material which is resistantto erosion, slag attack, and thermal shock.

In the preferred embodiment, the inner and outer members 54 and 56 ofthe tube 20 are both preferably molded from a batch made in severalsteps. In the first step the following ingredients, in the indicatedproportions by weight, are dry mixed in a muller-type mixer:

Percent 4 mesh kaolin calcine, RC 193-1 34.8 4 mesh RASC bauxite, RC260-1 17.7 35 mesh kaolin calcine, RC 376 17.2 35 mesh RASC bauxite, RC376 9.1 325 mesh A-2 alumina 7.6 Pulverized kaolin 8.5 Russell clay 4.0Bentonite 1.1

Russell clay is present in the mixture as a bloating clay to compensatefor shrinkage resulting from the presence of other ingredients such aspulverized kaolin, with the result that the tube wall is better able toresist the flow of pressurized air therethrough. Bentonite is a plasticclay which serves as a molding aid. And the main ingredients, kaolincalcine and bauxite, are refractory materials of high alumina contenthaving a high resistance to erosion and chemical attack by molten slag.

To the above dry mix is added 6% water and 1.25% of lignon-sulfonate, abinder commercially available as Additive-A from suppliers of refractorymaterials, so that by further mixing the wet mixture is prepared. Ifnecessary this mixture can be moisture sealed and stored for up to 48hours before use, or it can be used immediately, by ramming it in anupright core mold which is rotating as the mixture is added and rammedas fed to a density sufiiciently high to be gas impermeable andresistant to slag attack, yet without being so excessively dense as tobe prone to thermal shock failure. The molded members 54 and 56 are airdried, then fired in a periodic kiln in which the temperature isincreased over a 43 hour period to 2450 F. and held at this temperaturefor an additional 8 hours.

After firing and cooling, the tube components 54 and 56 are wetted withwater and assembled as shown in FIG. 1 with and inch elongated annularspace between them and the mortar slurry is poured from above into theannular space between the inner and outer members 54 and 56 to providethe mortar joint 62. The assembly is then dried at 200 to 250 F., afterwhich it is ready for use.

A suitable mortar is made by adding sufficient Water for the desiredconsistency to a mixture of the following ingredients, according to theweight percentages indicated:

Percent 35 mesh kaolin calcine, RC 376 25.0 35 mesh RASC bauxite, RC 37654.0 Hamilton No. 2 clay 11.0 Sodium silicate, brand GD 10.0

Optionally, 0.75% of Nodex-525 starch can be added to the mixture.

Although mixtures according to the percentage indicated are preferred,it is possible to deviate by using more or less than the amountspecified in making the tube of the present invention, with acceptableresults.

The pressure pouring tube hereinbefore described is seen to have anincreased wall thickness for the length thereof which is to be immersedin molten metal. The finished tube is distinguishable over prior artpouring tubes of the type employed in pressure casting molten steel inthat the portion thereof which is immersed in the melt is notmonolithically formed although it is made entirely of refractorymaterial. In addition, it should be noted that members 54 and 56 arefired after being dried, but after the members are assembled so as toform an annular space between them and a mortar slurry poured in thespace to join the members together, the pouring tube thus formed is notagain fired. That is, the mortar is not fired during the process ofmanufacturing the pouring tube. 1

It is well known in the art that a single specimen of known refractorycomposition shaped such as either member 54 or 56 and having a wallthickness of say two inches, is better able to withstand the thermalshock of immersion in a molten metal bath than a like member having agreater wall thickness. The maximum wall thickness of a monolithicallyformed tube is limited by the temperature of the melt and the materialfrom which it is made. With the disclosed type of construction the wallthickness can be significantly increased thereby increasing the life ofthe tube, so long as the individual members 54, 56 can individuallysurvive the thermal shock of immersion in the melt. It is well known inthe art that the finished tube is preheated to within approximately 1000F. of the temperature of molten steel before being immersed therein. Ifthe members 54 and 56 are of refractory composition and each is formedhaving a wall sufliciently thin to survive immersion in the steel melt,the assembled tube will also survive such immersion. Of course, itshould be appreciated that preheating is not necessary in the process ofmanufacturing the tube; may not be necessary prior to insertion inmolten metal other than steel; and may not be necessary if the tube isconstructed of other refractory materials. It is considered that thereason the pouring tube hereinbefore described is better able towithstand the thermal shock is because the individual members 54 and 56are able to move relative to one another. That is, the mortar flexesslightly or otherwise compensates for differential thermal expansion asthe tube adjusts to the temperature of the molten metal bath.

As disclosed in my copending patent application Ser. No. 506,095, filedNov. 2, 1965 for a Pressure Pouring Tube, the pressure casting apparatushereinbefore described may be said to comprise a ladle for containingmolten metal, an upright pouring tube having an inlet and its lower endin communication with a lower portion of the ladle and a dischargeoutlet at its upper end, and means for applying superatmosphericpressure to the molten metal within the ladle to force the molten metalupwardly through the pouring tube; the pouring tube comprising an innercylindrical member of substantially constant cross-section throughoutthe length thereof, and at least one outer cylindrical member receivingtherewithin the lower end of the inner cylindrical member and extendinglongitudinally of the tube from the lower end of the pouring tube toabove the level of the molten metal within the ladle, the pouring tubehaving a double wall provided by the member over at least the length ofthe tube that is immersed in the molten metal. Further, this pressurepouring apparatus may be provided wherein at least one of the members ofthe pressure pouring tube is made by molding and subsequently firing araw batch of finely divided dry ingredients consisting by weightessentially of about 33.3 to 40.3% of 4 mesh kaolin calcine, from 16.0to 19.5% of 4 mesh bauxite, from 15.5 to 18.9% of 35 mesh kaolincalcine, from 8.2 to 10.0% of 35 mesh bauxite, from 6.9 to 8.4% of -325mesh alumina, from 7.4 to 9.4% of pulverized kaolin, from 3.6 to 4.4% ofRussell clay, from 1.0 to 1.2% of bentonite, plus suificient water torender the batch flowable; the pouring tube, over the length thereofwhich is double-walled comprising an inner and outer tubular membersjoined together by a refractory mortar, the outer member being shorterthan the inner member; and the refractory mortar may be made by mixingwater to the desired consistency, with the following ingredients: from22.5 to 27.5% of 35 mesh kaolin calcine, from 48.6 to 59.4% of 35 meshbauxite, from 9.9 to 12.1% of Hamilton clay, and from 9 to 11% of sodiumsilicate.

The foregoing invention includes, in the process of forming a refractorypouring tube (made entirely of refractory materials) of the typeemployed in pressure casting molten metal from a ladle by applyingsuperatmospheric pressure to the surface of the metal to force itupwardly into the tube for discharge into a mold, a method of increasingthe wall thickness of the tube for the length of the tube which is to beimmersed in molten metal. The method generally includes or comprises thesteps of forming a tubular member of refractory composition within whichthe length of the aforesaid tube is receivable, firing the member soformed and assembling it with the tube so as to form an annular spacebetween them, and pouring a refractory mortar in the annular spacebetween the tube and member to join them together. The step of formingthe tubular member may include the step of ramming the refractorycomposition in a rotating core mold to a density sufficiently high to begas impermeable and resistant to slag attack without being soexcessively dense as to be prone to thermal shock. The process mayinclude the step of mixing a batch of refractory materials mainlyconsisting of bauxite and kaolin calcine with sufficient water to makethe refractory composition.

The process may be described as a process for forming a tube madeentirely of refractory material and immersible in molten steel,comprising, the steps of molding a first elongated annular member ofrefractory composition, molding a second elongated annular member ofrefractory composition and adaptable to receiving therewithin the end ofthe first member which is to be immersed in molten steel, assembling themembers so as to form an elongated annular space between them whichextends longitudinally of the length of the members and pouring arefractory mortar in the annular space to join the members together. Therefractory mortar is preferably made by mixing a mortar mainlyconsisting of bauxite and kaolin calcines with suflicient water to makeit pourable between the members.

What is claimed is:

1. A refractory pouring tube made of refractory materials, the tubebeing the type employed in pressure casting molten steel from a meltthereof by applying superatmospheric pressure to the surface of the meltto force it upwardly through the tube for discharge into a mold andcomprising,

(a) a fired inner tubular member of refractory composition having itsinner surface directly exposed to the melt,

('b) a fired outer tubular member of refractory composition within whichthe inner member is receivable so as to form an annular space betweenthem, the outer member having its outer surface directly exposed to themelt, the outer member extending longitudinally of the length of theinner member for at least the length of the tube which is to be immersedin the melt, and

(c) a refractory mortar in the annular space to join the outer surfaceof the inner member and the inner surface of the outer member directlytogether along the full length of the outer member, said refractorymortar being of the type permitting differential thermal expansionbetween the inner and outer members,

(d) each of said members being of suflicient wall thinness to resist thethermal shock of being immersed in the melt.

2. The tube according to claim 1 wherein the refractory compositionseach comprise a batch of ceramic refractory materials rammed to asufficient density to be gas impermea ble and resistant to slag attackwithout being so excessively dense as to be prone to thermal shockfailure.

3. The tube according to claim 1 wherein the refractory composition ofthe outer tubular member is a rammed batch of refractory materialsmainly consisting of bauxite and kaolin calcines with suflicient waterto make said refractory composition.

4. The tube according to claim 1 wherein the refractory composition ofthe outer tubular member is a rammed batch of refractory materialshaving a high resistance to slag attack and thermal shock mixed withsuflicient water to make said refractory composition.

5. A refractory pouring tube made of refractory materials, the tubebeing the type employed in pressure casting molten steel from a meltthereof by applying superatmospheric pressure to the surface of the meltto force it upwardly through the tube for discharge into a mold andcomprising, a fired inner tubular member of refractory composition, afired outer tubular member of refractory composition within which theinner member is receivable so as to form an annular space between them,and a refractory mortar in the annular space to join the memberstogether, said refractory mortar being of the type permittingdifferential thermal expansion between the inner and outer members, theouter member extending longitudinally of the length of the inner memberfor at least the length of the tube which is to be immersed in moltensteel and comprising a plurality of annular members ar ranged in seriesto receive the inner member therewithin.

6. A tube made entirely of refractory materials only which extendslongitudinally of the entire length of the second member, and arefractory mortar entirely filling the annular space to join the memberstogether, each of the annular members being of sufficient wall thinnessto resist the thermal shock of being immersed in molten steel, saidrefractory mortar being of the type permitting differential thermalexpansion between the inner and outer members, the wall thickness of thetube for at least the length thereof which is to be immersed in moltensteel being greater than the maximum wall thickness of a monolithicallyformed refractory tube which is able to withstand the thermal shock ofbeing immersed in molten steel.

7. The tube according to claim 6 wherein the annular members are firedmembers,

8. The tube according to claim 6 wherein the refractory composition ofthe second annular member is a fired batch of refractory materialsrammed to a density sufficiently high to be gas impermeable andresistant to slag attack without being so excessively dense as to beprone to thermal shock failure.

9. The tube according to claim 6 wherein the refractory mortar is madefrom a mix of mainly bauxite and kaolin calcines with sufiicient waterto make the mix flowable.

10. The tube according to claim 6 wherein each of the members is a firedmolded member of suflicient density to be gas impermeable without beingso excessively dense as to be prone to thermal shock failure.

11. A tube made entirely of ceramic refractory materials and immersiblein molten steel, comprising, a first annular member of ceramicrefractory composition, a second annular member of ceramic refractorycomposition adaptable to receiving therewithin the end of the firstmember which is to be immersed in molten steel, the members assembled soas to form an annular space therebetween which extends longitudinally ofthe length of the tube, and a refractory mortar entirely filling theannular space to join the members together, said refractory mortar beingof the type permitting differential thermal expansion between the innerand outer members, the outer member comprising a plurality of annularmembers arranged in series to receive the inner member therewithin.

References Cited UNITED STATES PATENTS 10/1966 Yates.

7/1967 Miller 164-309 U.S. Cl. X.R.

